System and method of communicating a priority indication in a call control/bearer control telecommunication system

ABSTRACT

The present invention relates generally to telecommunication services, and in particular, to communicating priority indications between telecommunication nodes in a telecommunication system having a separated call control and bearer control architecture. The present invention provides a number of solutions which map or assign the call level priority to the bearer level.

FIELD OF INVENTION

The present invention relates generally to telecommunication servicesand, in particular, to communicating priority indications betweentelecommunication nodes in a telecommunication system having a separatedcall control and bearer control architecture.

BACKGROUND ART

For cost-efficiency reasons telecommunication operators are increasinglydeploying non-STM (non-Synchronous Transfer Mode) transport technologiesinside their networks. Examples of these technologies are ATM(Asynchronous Transfer Mode), IP (Internet Protocol), and FR (FrameRelay). Therefore, a standardised solution is required to supportexisting services of today's public telecommunication networks overmulti-vendor non-STM infrastructures. In the current publictelecommunication networks, the call control (CC) and bearer control(BC) are tightly coupled in the same public network protocol, forexample, ISUP (ISDN User Part). As a result of this trend to run overmulti-vendor non-STM infrastructures, a new network architecture hasbeen developed that allows for the splitting or separating of callcontrol (CC) and bearer control (BC) into separate protocols. FIGS. 1 aand 1 b show the evolution from current integrated CC/BC public networkprotocols such as ISUP, to the separated CC/BC solution.

The split of CC and BC functions results in a new interface exposedbetween the CC function and BC function. A protocol is required toenable the coupling between the CC and BC functions when atelecommunications node is implemented in a separated environment. As anexample, the International Telecommunications Union-TelecommunicationsSector (ITU-T) and the Internet Engineering Task Force (IETF) havedefined a Gateway Control Protocol to enable the coupling between the CCand BC functions. This protocol is designed to control multimediaconnections from a remote control entity and operatively resides betweenthe CC functionality and the BC functionality, as shown in FIGS. 1 a and1 b. Variants of this protocol are known as H.248 and Q.1950 in the ITU,and Megaco in the IETF.

As a result of the separation of Call Control and Bearer Control, anumber of functions which existed in the integrated CC/BC environmentrequire the functionality to be duplicated in the Call Control and theBearer Control environment. One such function is the “Priority Call”function, which is used, for example, in emergency call situations. Thedefinition of the “Priority Call” function may be found in ITU-TRecommendation I.255.4, Priority Service. In such emergency situations,it is absolutely necessary for emergency calls to progress, but it isnot necessary that normal calls progress. Typically, this could beachieved in, for example, one of two ways.

Firstly, if a node receives an emergency call and it has reached itslimit of call throughput, the way to allow this emergency call toprogress would be to sacrifice, that is terminate, an existing normalcall to free up the resources required for the emergency call. Secondly,a node may reserve a certain percentage, for example 2%, of itsresources for use by emergency calls only. This means that normal callscannot use those particular resources. The consequence of this is thatin non-emergency situations, the node is running at a sub-optimalcapacity. In the example given in this case, 98%. In both of the aboveexamples, it is necessary for the emergency call to be marked as apriority call so that the node can identify the emergency call as such.In the separated CC/BC architecture discussed above, this applies toboth call and bearer control protocols, as illustrated in FIG. 2.

In the network configuration of FIG. 2, the call and bearer connectionsare initiated at Node 1 and terminated at Node 5. The call controltraverses the network via Node 3 or path C1-C2 as shown, whereas thebearer control traverses the network via Nodes 2 and 4 or path B1-B2-B3as shown. To illustrate the emergency call scenario, it is assumed thatall nodes and paths are running at or near to full capacity foremergency calls, and a certain percentage of resources on all nodes andpaths are reserved for emergency calls. In this particular example, Node1 initiates an emergency call, and, since it is running at fullcapacity, it may not use the normal call set up paths. Hence, it selectsa path for both the Call Control and Bearer Control, which is reservedfor emergency calls, that is, path C1 and path B1, respectively.Similarly, Node 3 should recognise the call as an emergency call andselect its internal resources and outgoing path to Node 5 or path C2,appropriately. Likewise, Node 2 should recognise the fact that thebearer path being requested is related to an emergency call, and thusshould select its internal resources and outgoing path to Node 4 or pathB2, appropriately.

In a separated CC and BC architecture, only the Call Control protocolhas an indication that the call has a certain priority. One method oftransporting this priority information in the protocol is by the BICC(Bearer Independent Call Control) Precedence indication.

BICC is based on ISUP (Integrated Services Digital Network User Part.That is, the control part of the Signalling System No. 7 protocol, SS7),which is a combined CC/BC protocol. MLPP (Multi-Level Precedence andPreemption Service) is a function in BICC/ISUP. A detailed descriptionof the MLPP is found at ITU-T Recommendation I.255.3 Multi-levelPrecedence and Preemption Service (MLPP), and ITU-T RecommendationQ.1902.3, Bearer independent call control protocol (CS2) and SignallingSystem No. 7—ISDN user part formats and codes.

There are currently five Precedence values defined in the BICC protocol,namely flash-override, flash, immediate, priority and routine, which areassigned values 0 to 4 respectively. The Call Control protocol providesfor an indication of call priority. Currently the only way Node 2, orNode 4, is aware that the requested bearer set-up is related to anemergency call is that the request is entered on path B1 (or B2). Thisrequires path reservation at a call set up. It thus requires priornetwork configuration knowledge in Node 2, and also Node 4, which is notalways possible or practical in modern switching and non-switchingnetworks, and may require complicated Operation and Maintenanceprocedures

It is an object of the present invention to overcome or ameliorate atleast one of the problems of the prior art.

SUMMARY OF INVENTION

In one aspect, the present invention provides in a separated callcontrol, bearer control telecommunications network, a method ofcommunicating a call control level priority indication between a firsttelecommunications node and a second telecommunications node via thebearer network including the steps of:

-   -   1) determining a call control level priority indication;    -   2) assigning a bearer level priority indication to a priority        indication field in a bearer network protocol message in        accordance with a priority level of a bearer network protocol;    -   3) transmitting the bearer network protocol message within the        bearer network via bearer network nodes intermediate the first        and second telecommunication nodes.

Preferably, the bearer level indication corresponds to the call controllevel indication.

In essence, the present invention stems from the realisation thatassigning, in accordance with a dedicated relationship, a call controllevel priority indication to a bearer priority indication in a bearernetwork protocol message field in accordance with a priority mechanismof the bearer network protocol, allows for an explicit indication ofpriority at the bearer level in a separated network architecture. Thus,a solution is provided which maps or assigns the call level priority,for example in the form of the BICC Precedence values, to the bearerlevel.

The call control level priority indication is preferably determined fromat least one of a call set up message, and, a subscriber profile.

In another aspect, the present invention provides in a telecommunicationsystem having separated Call Control and Bearer Control architecture:

-   -   a method for enabling transmission of a call control level        priority indication along at least a portion of a path of        communication established between a first telecommunication node        and a second telecommunication node, the path of communication        including at least one bearer network node,    -   the method including:    -   mapping, in accordance with a dedicated relationship, a call        control level priority indication to a bearer priority        indication in a bearer network protocol message field in        accordance with the following steps:    -   a) determining a Bearer Independent Call Control priority value;    -   b) determining a priority level in a bearer network for a        message to be communicated in the bearer network based on the        determination in step a).

In a further aspect, the present invention provides in atelecommunication system, the system including a separated Call Controland Bearer Control architecture between a first telecommunication nodeand a second telecommunication node, an improvement including:

-   -   1) call control level priority determining means adapted to        determine a call control level priority indication;    -   2) logic means adapted to logically map the call control level        priority indication to a priority indication field in a bearer        network message in accordance with a priority level of a bearer        network protocol;    -   3) a transmitter adapted to transmit the bearer network protocol        message within a bearer network via bearer network nodes        intermediate the first and second telecommunication nodes.

In yet another aspect, the present invention provides a network node ofa telecommunication system, the system including a separated CallControl and Bearer Control architecture, the node including:

-   -   1) call control level priority determining means adapted to        determine a call control level priority indication;    -   2) logic means adapted to logically map the call control level        priority indication to a priority indication field in a bearer        network protocol message in accordance with a priority level of        a bearer network protocol.

In another aspect, the present invention provides a bearer networkprotocol data unit for use in a telecommunications system having aseparated Call Control and Bearer Control architecture, the bearerprotocol data unit including:

-   -   a data payload field for communicating user data, and    -   at least one header field including a priority indication field        serving to provide a priority designation of the bearer protocol        data unit, characterised in that, the priority indication field        includes an attribute based on a call control level priority        indication for a call set up message.

In still another aspect, the present invention provides a computerprogram product including:

-   -   a computer usable medium having computer readable program code        and computer readable system code embodied on said medium for        transliterating a call control message between a first node and        a second node within a telecommunication system via a bearer        network in a separated call control and bearer control        telecommunication network, said computer program product        including:    -   computer readable code within said computer usable medium for:    -   determining a call control level priority indication for a call        set up message, and    -   mapping, in accordance with a dedicated relationship, a call        control level priority indication to a bearer priority        indication in a bearer network protocol message field in        accordance with a priority mechanism of a bearer network        protocol.

The call control level priority indication, in a preferred embodiment isassigned to a received call set up message. In another preferredembodiment, the call control level priority indication is assigned inaccordance with a subscriber profile.

The method of the present invention may further include the steps of:

-   -   allocating internal resources of the bearer network for        communicating the bearer network protocol message dependent on        the bearer level priority indication.

Further, the step of determining the call control level priorityindication or the step of assigning a corresponding call control levelpriority indication may be performed at the first telecommunication nodeor at any node or nodes intermediate the first and second nodes.

Preferably, at least one of the call control level indication or thecorresponding call control level indication is determined in accordancewith a first or second predetermined designation, respectively. Thefirst designation is, preferably, a call control protocol indication andthe second designation is, preferably, a bearer protocol indication orbearer control protocol indication.

Preferably, the call control protocol is the Bearer Independent CallControl (BICC) and the call control level priority indication is anI.255.3 Multi-level Precedence and Pre-emption Service (MLPP)indication, or a new field based on the requirements from the I.255.4Priority Service.

In one example, the bearer network may be a switched ML2 bearer networkand the bearer network protocol message may be a Q2630.2 ML2 ERQmessage. In another example the bearer network may be a non-switchedbearer network and the bearer network protocol message may transmittedby at least one Ipv4 or Ipv6 packet.

DESCRIPTION OF PREFERRED EMBODIMENT

A preferred embodiment of the present invention will now be describedwith reference to the accompanying drawings, in which:

FIGS. 1 a and 1 b show the evolution from previous integrated CallControl and Bearer Control public network protocols to a separated CallControl and Bearer Control public network architecture.

FIG. 2 shows a separated Call Control and Bearer Control networkarchitecture of the prior art.

FIG. 3 shows an example of call level priority indications communicatedvia a bearer network in accordance with a first preferred embodiment ofthe present invention.

FIG. 4 shows an example of call level priority indications communicatedvia a bearer network in accordance with a second preferred embodiment ofthe present invention.

An indication of call control level priority may be determined on a callby call basis or in accordance with a predesignated subscriber profile.In the call by call basis example, the call control level priorityindication is determined from a call set up message.

There are two types of bearer network configurations available in theexisting telecommunication network specifications of the separated CCand BC architecture. These are switched and non-switched networks. Aswitched network is one where the bearer path is defined at the time ofcall set-up, and all user data is transferred along that path for theduration of the call. A non-switched network is one whereby the bearerpath is not defined at call set-up, and decisions are made in real-timeas to the path that user data is communicated. An example of a switchednetwork is one where the bearer is MAI (ATM Adaption layer 2), wherebythe bearer is connected through one or more AAL2 switches and the pathof the user packets through the switches is defined at the time of callset-up. Detail on the AAL2 bearer protocol is found at ITU-TRecommendation Q.2630.2, AAL Type 2 Signalling Protocol. Furtherexamples of possible bearer control protocols for a switched network asin a switched BICC network include, ML1 (ATM Adaption Layer 2), PNNI(Private Network to Network Interface), DSS2 (Digital SubscriberSignaling #2 for ATM broadband signaling), B-ISUP (Broadband ISUP). Anexample of a non-switched network is one where the bearer is IP(Internet Protocol), where the user packets are transferred through IProuters, where the path of the user packets through the network isdecided by the IP routers in real-time. Detail on the IP bearer protocolis found, for example, at RFC791, Internet Protocol (Ipv4). In anon-switched network, each packet takes a different path through the IPnetwork. Further examples of possible bearer protocols for anon-switched network, as in a non-switched BICC network include,Structured AALL (see I.363.1) and Trunked ML2 (see Q.2630.1, Annex A). Aperson skilled in the art would recognise that other bearer networkprotocols can be used in associated with the invention, withoutdeparting from the spirit of the present invention.

Switched Network

In a switched bearer network such as an AAL2 switched network, theBearer Control Protocol is carried through and processed at the switchesin the bearer network. The Bearer Control Protocol carries a priorityindication through the bearer network in the bearer establishmentmessage in order for each switch to recognise the priority of the call.This can be of the form of, say a value of 0-4, with 4 indicatinghighest priority and 0 indicating lowest priority. Referring to FIG. 3,in the AAL type 2 signalling protocol, this is preferably in the simpleform of a value of 0 to 4 in the ERQ message. Nodes in the bearernetwork use this value to allocate internal resources and outgoing pathsaccording to particular network conditions. For example, Node 2 canimmediately recognise the priority level from the incoming message androute the call to Node 4 along an “emergency-marked” path between thetwo nodes.

In the present invention, the call control level priority indication isdetermined and assigned or mapped to a bearer level priority indicationfield in a bearer network protocol message. In one form, the value ofthe priority indicator in the Q.2630.2 ERQ message is mapped from theBICC Call Control Priority value. This mapping is done in the initiatingnode, Node 1. In other preferred embodiments, the invention is embodiedby the mapping being performed at any one or a combination of node(s)intermediate a first transmitting node or endpoint and a secondreceiving node or endpoint for the call. Table 1, below illustrates thismapping. TABLE 1 BICC Call Control Priority Value Bearer ControlPriority (e.g. MLPP value) Value (e.g. in Q.2630) Flash Override (0) 0Flash (1) 1 Immediate (2) 2 Priority (3) 3 Normal (4) 4

Whilst the values can be mapped exactly, it is also within the scope ofthe invention to set the CC and BC Priority values to different valuesaccording to the importance of the particular priority call, networkconfiguration, and current network usage. The person skilled in the artwould derive variants without limiting the scope of the invention.

Non-Switched Network

In a non-switched network, such as an IP network, the Bearer ControlProtocol is carried, or tunnelled inside the Call Control Protocol.Detail on an example Bearer Control Protocol for IP networks is found atITU-T Recommendation Q.1970, BICC IP Bearer Control Protocol. The BearerControl Protocol is not passed through the bearer network, that is, itis not seen by the routers in the bearer network. The protocol allocatesresources in the network. Due to the nature of a non-switched network,each user packet, in this case IP packet, carries an indication of thepriority in order for each router to be able to route the packetaccording to the priority. Other bearer control protocols can be used aswould be understood by a person skilled in the art.

In order to obtain the full priority indication required, which issimilar to that of a switched network, the call control level priorityindication is determined and then assigned or mapped between the BICCCall Control Priority values and the values carried in the IP packet. Afield already exists in the IP header, as an example see RFC791,Internet Protocol (Ipv4), which carries this priority, an 8-value fieldcalled “Priority”. This is, in turn, carried inside the “Type ofService” field. An example of this mapping is shown below in table 2.

As in the example of a switched Network, the present invention may beembodied by this mapping being performed at, or by means within theinitiating or transmitting node, for example Node 1. In anotherpreferred embodiment, the invention may be embodied by the mapping beingperformed at any one or a combination of node(s) intermediate a firsttransmitting node or endpoint and a second receiving node or endpointfor the call. TABLE 2 BICC Call Control Priority Value IP PrecedenceValue (e.g. in IP (e.g. MLPP value) Header, Type of Service field) FlashOverride (0) Flash Override (4) Flash (1) Flash (3 Immediate (2)Immediate (2) Priority (3) Priority (1) Normal (4) Routine (0)

As a further example, there are three further values of the IPPrecedence field, namely “Network Control (7)”, “Internetwork Control(6)”, and “CRITIC/ECP (5)” that are not used in the above tabledexample. However it is possible to define a mapping from a specific BICCpriority value to one of these values. For example, a BICC Priorityvalue for Flash Override (0), is mapped to an IP Priority value forNetwork Control (7). As in the switched network case, the specifics ofthis mapping are in accordance with the importance of the particularpriority call, network configuration, and current network usage.

The call control level priority indication is determined by a firstdesignation. The bearer level priority indication is determined by asecond designation. Tables 1 and 2 above provide examples. Furthermore,the first designation can be a BICC indication and the seconddesignation can be a bearer network control Protocol indication. Askilled person would understand that variations are possible within thescope of the present invention.

In a further embodiment of the present invention, the call controlpriority level indication is processed from the bearer network level tothe call control network level by way of decoding/recovery in which thebearer network priority level is determined and assigned to a callcontrol level priority indication of a call, call message or assigned inaccordance with a subscriber profile. This process is performed at asecond or receiving node or endpoint. In a further embodiment, theprocess is performed at a node(s) intermediate a first transmitting nodeand a second receiving node where the intermediate node provides a CallControl function.

As the present invention may be embodied in several forms withoutdeparting from the spirit of the essential characteristics of theinvention, it should be understood that the above described embodimentsare not to limit the present invention unless otherwise specified, butrather should be construed broadly within the spirit and scope of theinvention as defined in the appended claims. Various modifications andequivalent arrangements are intended to be included within the spiritand scope of the invention and appended claims.

1. In a separated call control, bearer control telecommunicationsnetwork, a method of communicating a call control level priorityindication between a first telecommunications node and a secondtelecommunications node via the bearer network comprising the stepsof: 1) determining a call control level priority indication; 2) mappingthe call control level priority indication to a bearer level priorityindication of a priority indication field in a bearer network protocolmessage in accordance with a priority level of a bearer networkprotocol; 3) transmitting the bearer network protocol message within thebearer network via bearer network nodes intermediate the first andsecond telecommunication nodes.
 2. A method as claimed in claim 1,wherein the call control level priority indication is determined from acall set up message.
 3. A method as claimed in claim 1, wherein the callcontrol level priority indication is determined from a subscriberprofile.
 4. A method as claimed in claim 1, further comprising the stepof: allocating internal resources of the bearer network forcommunicating the bearer network protocol message dependent on thebearer level priority indication.
 5. A method as claimed in claim 1,wherein at least one of the steps of determining the call control levelpriority indication and mapping the call control level priorityindication to a bearer level priority indication is performed at thefirst telecommunication node.
 6. A method as claimed in claim 1, whereinat least one of the steps of determining the call control level priorityindication and mapping the call control level priority indication to abearer level priority indication is performed at a node(s) intermediatethe first node and the second node.
 7. A method as claimed in claim 1,wherein the bearer network is a switched bearer network and the bearernetwork protocol message is a switched bearer network protocol message.8. A method as claimed in claim 1, wherein the bearer network is anon-switched bearer network and the bearer network protocol message is anon-switched bearer network protocol message.
 9. A method as claimed inclaim 1 wherein, the call control level priority indication isdetermined in accordance with a first predetermined designation.
 10. Amethod as claimed in claim 1, wherein, the bearer level priorityindication is determined in accordance with a second predetermineddesignation.
 11. A method as claimed in claim 9, wherein the firstpredetermined designation is a Bearer Independent Call Control (BICC)protocol indication and the call control level priority indication is atleast one of a Multi-level Precedence and Preemption Service (MLPP)indication, and an indication based on requirements of a PriorityService.
 12. A method as claimed in claim 10, wherein the secondpredetermined designation is at least one of a bearer network controlprotocol indication, and a bearer network protocol indication and thecall control level priority indication is at least one of a Multi-LevelPrecedence and Preemption service (MLPP) indication, and an indicationbased on requirements of a Priority Service.
 13. A network node of atelecommunication system, the system including a separated Call Controland Bearer Control architecture, the node comprising: 1) call controllevel priority determining means adapted to determine a call controllevel priority indication; and 2) logic means adapted to logically mapthe call control level priority indication to a priority indicationfield in a bearer network message in accordance with a priority level ofa bearer network protocol.
 14. A network node as claimed in claim 13,wherein the call control level priority indication is determined from acall set up message.
 15. A network node as claimed in claim 13, whereinthe call control level priority indication is determined from asubscriber profile.
 16. A network node as claimed in claim 13, whereininternal resources of the bearer network for communicating the bearernetwork protocol message are allocated dependent on the bearer levelpriority indication.
 17. (Cancelled)
 18. A network node as claimed inclaim 13, wherein the bearer network ia a switched bearer network andthe bearer network protocol message is a switched bearer networkprotocol message.
 19. (Cancelled)
 20. A network node as claimed in claim13, wherein the call control level priority indication is determined inaccordance with a first predetermined designation.
 21. A network node asclaimed in claim 13, wherein the bearer level priority indication isdetermined in accordance with a second predetermined designation.
 22. Anetwork node as claimed in claim 20, wherein the first predetermineddesignation is a Bearer Independent Call Control (BICC) protocolindication and the call control level priority indication is at leastone of a Multi-level Precedence and Pre-emption Service (MLPP)indication, and an indication based on requirements of a PriorityService.
 23. A network node as claimed in claim 21, wherein the secondpredetermined designation is at least one of a bearer network controlprotocol indication and a bearer network protocol indication and thecall control level priority indication is at least one of a Multi-levelPrecedence and Pre-emption Service (MLPP) indication, and an indicationbased on requirements of a Priority Service.
 24. A computer programapparatus including: a computer usable medium having computer readableprogram code and computer readable system code embodied on said mediumfor transliterating a call control message between a first node and asecond node within a telecommunication system via a bearer network in aseparated call control and bearer control telecommunication network,comprising: computer readable code within said computer usable mediumfor: determining a call control level priority indication for a call setup message, and mapping, in accordance with a dedicated relationship, acall control level priority indication to a bearer priority indicationin a bearer network protocol message field in accordance with a prioritymechanism of a bearer network protocol.
 25. A computer program apparatusas claimed in claim 24, wherein the call control level priorityindication is determined from the call set up message.
 26. A computerprogram apparatus as claimed in claim 24, wherein the call control levelpriority indication is determined from a subscriber profile.
 27. Acomputer program apparatus as claimed in claim 24, said computer programproduct further including computer readable code within said computerusable medium for allocating internal resources of the bearer networkfor communicating the bearer network protocol message dependent on thebearer level priority indication.
 28. A computer program apparatus asclaimed in claim 24, wherein at least one of the steps of determiningthe call control level priority indication and mapping the call controllevel priority indication to a bearer level priority indication ispreformed at the first telecommunication node.
 29. A computer programapparatus as claimed in claim 24, wherein at least one of the steps ofdetermining the call control level priority indication and mapping thecall control level priority indication to a bearer level priorityindication is preformed at a node(s) intermediate the first node and thesecond node.
 30. A computer program apparatus as claimed in claim 24,wherein the bearer network is a switched bearer network and the bearernetwork protocol message is a switched bearer network protocol message.31. (Cancelled)
 32. A computer program apparatus as claimed in claim 24,wherein the call control level priority indication is determined inaccordance with a first predetermined designation.
 33. A computerprogram apparatus as claimed in claim 24, wherein the bearer levelpriority indication is determined in accordance with a secondpredetermined designation.
 34. A computer program apparatus as claimedin claim 32, wherein the first predetermined designation is a BearerIndependent Call Control (BICC) protocol indication and the call controllevel priority indication is at least one of a Multi-level Precedenceand Pre-emption Service (MLPP) indication, and an indication based onrequirements of a Priority Service.
 35. A computer program apparatus asclaimed in claim 33, wherein the second predetermined designation is atleast one of a bearer network control protocol indication, and a bearernetwork protocol indication and the call control level priorityindication is at least one of a Multi-level Precedence and Pre-emptionService (MLPP) indication, and an indication based on requirements of aPriority Service.